This invention relates generally to a new and improved die cylinder assembly for use in a press or the like. The die cylinder assembly is used to cushion movement of a die member holding a workpiece, when the workpiece is being formed by another die member.
A known die cylinder assembly is disclosed in U.S. Pat. No. 4,111,030. This known die cylinder operates in an environment which contains fluids such as die lubricants, dirt and other contaminating materials. These contaminants may tend to work their way in between the piston and cylinder of the die cylinder assembly. This increases wear and decreases operating life of the assembly.
In this known die cylinder assembly, the cylinder chamber is divided into a variable volume head end chamber and a variable volume rod end chamber. High pressure nitrogen, the working fluid in the head end chamber, resists movement of the piston upon operation of the press, to cushion piston movement. The rod end chamber is located near the end wall of the cylinder where the piston rod emerges from the cylinder. As the piston rod retracts into the cylinder, the rod end chamber expands and a reduced pressure is created therein. This tends to draw contaminants in between the piston rod and cylinder and into the rod end chamber.
In an attempt to eliminate this problem, the rod end chamber of this known die cylinder assembly is vented away from the die cylinder assembly by tubing. The tubing leads to a source of clean ambient air free of contaminants. Alternatively, the tubing leads to a supply of clean compressed air at a pressure slightly above ambient pressure.